Fix LD_PRELOAD (#184)

- __libc_start_main in libomnitrace-dl wasn't wrapping bc of -fvisibility=hidden
- fix OMNITRACE_STRIP_TARGET
- omnitrace_reset_preload function in main library
- defer removing libomnitrace from LD_PRELOAD

source/bin/omnitrace-sample/CMakeLists.txt

@@ -17,6 +17,8 @@ set_target_properties(
     omnitrace-sample PROPERTIES BUILD_RPATH "\$ORIGIN:\$ORIGIN/../${CMAKE_INSTALL_LIBDIR}"
                                 INSTALL_RPATH "${OMNITRACE_EXE_INSTALL_RPATH}")
 
+omnitrace_strip_target(omnitrace-sample)
+
 install(
     TARGETS omnitrace-sample
     DESTINATION ${CMAKE_INSTALL_BINDIR}